Drug delivery devices for setting and dispensing multiple doses of a liquid medicament are as such well-known in the art. Generally, such devices have substantially a similar purpose as that of an ordinary syringe.
Drug delivery devices, in particular pen-type injectors have to meet a number of user specific requirements. For instance, with patients' suffering a chronic disease e.g. diabetes, the patient may be physically infirm and may also have impaired vision. Therefore, suitable drug delivery devices need to be robust in construction and should be easy to use. Furthermore, manipulation and general handling of the device and its components should be intelligible and understandable. Moreover, a dose setting and a dose dispensing procedure must be easy to operate and unambiguous. When the device is of disposable type, it should be inexpensive to manufacture and easy to dispose. In order to meet these requirements, the number of parts and steps required to utilize the device should be kept to a minimum.
In particular, disposable devices, that are intended to be discarded after consumption of the medicament contained therein, are provided in form of a container having numerous, substantially identical drug delivery devices disposed therein. In a practical application scenario, a user may for instance be disturbed in the process of preparing the drug delivery device for a subsequent medicament dispensing procedure. In particular, the user may already have removed a protective cap from the device. When disturbed, the user may return the removable cap to its initial position and may also return the drug delivery device into the container. Upon a resumption of the dose setting and/or dispensing procedure later on, the user may no longer identify the particular drug delivery device he initially intended to use.
It is therefore an object of the present invention to provide a drug delivery device which is adapted to indicate to a user, if the device has been used before. According to another object, the device is intended to enhance patient safety and to protect the contents of the device from contamination when stored. Consequently, the invention intends to prolongate sterile conditions and the shelf life of a drug delivery device in storage.